Optical waveguide circuit

Abstract

The present invention relates to an optical waveguide circuit such as an arrayed waveguide grating, etc. A lower cladding is formed on a silicon substrate. A core having the following waveguide construction is formed thereon. That is, an input side slab waveguide is connected to the emission side of a plurality of incidence waveguides, a plurality of arrayed waveguides having different lengths form each other are juxtaposed at and connected to the emission side thereof, an output side slab waveguide is further connected to the emission side thereof, and a plurality of emission waveguides are connected to the emission side thereof, thereby causing the abovementioned waveguide construction. The upper cladding covers up the core. The cladding and core are made of silica-based glass, wherein the value B of birefringence occurring in said optical waveguide portion is |B|<=5.34x10-5, and alphas-2.0x10-7<=alphag <=alphas+2.0x10-7 is established where it is assumed that the thermal expansion coefficient of the upper cladding is alphag, and the thermal expansion coefficient of a silicon substrate is alphas.

What is claimed as new and desired to be secured by Letters Patent of United States is:  
     
       1. An optical waveguide comprising: 
       an optical waveguide portion formed on a silicon substrate and including a lower cladding, a core, and an upper cladding formed of silica-based glass, wherein a value B of birefringence occurring in said optical waveguide portion is |B|≦5.34×10 −5 .  
     
     
       2. An optical waveguide according to  claim 1 , wherein:. 
       the upper cladding has a thermal expansion coefficient αg,  
       the silicon substrate has a thermal expansion coefficient αs, and  
       αs−2.0×10 −7 ≦αg≦αs+2.0×10 −7 .  
     
     
       3. An optical waveguide circuit comprising: 
       an optical waveguide portion formed on a silicon substrate and including  
       a lower cladding,  
       an upper cladding, and  
       a core, including  
       a first slab waveguide connected to an emission side of one or more juxtaposed optical input waveguides,  
       a plurality of juxtaposed arrayed waveguides, having wavelengths different from each other and configured to propagate light introduced from said first slab waveguide, connected to an emission side of said first slab waveguide,  
       a second slab waveguide connected to an emission side of said plurality of arrayed waveguides, and  
       a plurality of juxtaposed optical output waveguides connected to an emission side of said second slab waveguide,  
       wherein said optical input waveguides are configured to output a plurality of optical signals having wavelengths different from each other, said arrayed waveguides are configured to propagate said optical signals with a difference in phase for each wavelength, and said optical output waveguides are configured to input said optical signals differing by wavelength, and  
       said lower cladding, said core, and said upper cladding being formed of silica-based glass, wherein a value B of birefringence occurring in said optical waveguide portion is |B|≦5.34×10 −5 .  
     
     
       4. An optical waveguide circuit according to  claim 3 , wherein: 
       the upper cladding has a thermal expansion coefficient αg,  
       the silicon substrate has a thermal expansion coefficient αs, and  
       αs−2.0×10 −7 ≦αg≦αs+2.0×10 −7 .